A programmable controller is described in Siemens Catalog ST 70, 1995. With a programming unit, a user creates a program for controlling an industrial process, including software function blocks, e.g., in the form of organization blocks, program blocks and entity data blocks. The programmable controller is connected to the programming unit by a bus system over which the programming unit transmits the control program to the programmable controller. Furthermore, an operating and monitoring device which is provided for process management can also be connected to the bus system, making it possible to display process images that incorporate multiple image objects.
It is frequently necessary for software function blocks of a control program to be transmitted from a programmable controller of a manufacturing site or from a software pool of this manufacturing site to a programmable controller of another manufacturing site. In particular, when the manufacturing sites are a great distance apart, e.g., because of globalization of manufacturing activities, these software function blocks are transmitted over the Internet, a global network. This requires servers with suitable communications interfaces which permit the use of the Internet communications protocol as well as the communications protocol of the programmable controller. On the basis of these different protocols and the architecture of the programmable controllers, it is impossible to tie in the software function blocks while the control program is running, especially when programmable controllers of different manufacturers are to be supplied with these software function blocks.